The present invention relates to liquid dispensing apparatus and pertains particularly to an improved infusion apparatus for delivering intravenous drugs at a controlled rate to a patient.
It is often necessary to intravenously supply patients with pharmaceutically active liquids at a controlled rate over a long period of time. It is desirable that this be accomplished while the patient is in an ambulatory state. A few devices have been developed in the past for accomplishing this purpose.
The prior art devices typically comprise an elastic bladder forming a liquid container mounted in an elongated cylindrical housing, and having a flow control valve or device and tubing for supply of the liquid to the patient. These devices are constructed with the cylindrical form in order to provide a compact arrangement. The elastic walls of the bladder are forced to expand along the walls of the cylindrical housing when filled with the liquid, and provide the pressure for expelling the liquid. These prior art devices are typically filled by hand by means of a syringe which often require an inordinate amount of force.
Another drawback to the prior art devices is that the bladder is forced to expand into an unnatural elongated configuration along the housing walls as the container is filled. As a result of this unnatural configuration, the pressure of the bladder and the flow rate of the unit varies widely with the volume of liquid therein. Therefore, they do not have a reasonably stable pressure and flow rate over the infusion period.
Prior U.S. Pat. Nos. 5,080,652, dated Jan. 14, 1992 and 5,105,983, dated Apr. 21, 1992 of common assignment herewith disclose recently developed improved infusion devices. These devices have an inflatable elastic bladder that is allowed or inflate naturally at a substantially uniform pressure. A hard protective housing accommodates natural spherical inflation of the bladder to its rated capacity or volume.
While these improved devices are portable and convenient to use, one objection is that the housing is rigid and space consuming. This increases the cost of packaging, storage and shipment. It also increases the cost of manufacture because the housing must also be sterilized. Therefore, it would be desirable to have a housing that is collapsible and/or reusable.
It is desirable that the housing of an inflatable bladder infuser be compact and inexpensive to manufacture and ship.
Accordingly, it is desirable that an improved infuser apparatus be available.